Leica Lens Design Insight

[Richard Clompus <rclompus@voicenet.com>]

Dear Fellow LUGnuts,

Something occurred to me today and I thought I'd ask members of the group
who are more knowledgable than me on camera lens design.  

In reviewing the original 35mm Summicron vs. the 35mm Summilux, the lenses
are both composed of 7 elements in 5 groups.  Barrels look almost the same
and the weights are relatively close.  The aperture blades on my Summicron
don't open up all the way - as if there is another 1/2 f stop hiding in
there.  I noticed the same failure to fully open on my 21mm Elmarit - like
the lens could have been capable of being a f 2.4 or f 2.2 but Leica
limited the aperture blades so that the lens would only perform as a 2.8 lens.

I wonder whether Leitz went through a deisgn phase where they put together
the 35mm f2 and then said "well, if we make the lenses a little bit larger
in diameter, we can squeeze a f 1.4 lens out of this design also.

Interesting thought.

Richard Clompus, OD